Made some progress

config/environments/development.rb

@@ -38,4 +38,6 @@ Rails.application.configure do
 
   # Raises error for missing translations
   # config.action_view.raise_on_missing_translations = true
+
+  config.action_mailer.default_url_options = { host: ENV['NGROK_HOST'] }
 end

config/initializers/ostatus.rb

@@ -0,0 +1 @@
+LOCAL_DOMAIN = ENV['LOCAL_DOMAIN'] || 'localhost'

config/routes.rb

@@ -1,3 +1,11 @@
 Rails.application.routes.draw do
+  get '.well-known/host-meta', to: 'xrd#host_meta', as: :host_meta
+  get '.well-known/webfinger', to: 'xrd#webfinger', as: :webfinger
+
+  get 'atom/:id',   to: 'atom#user_stream', as: :atom_user_stream
+  get 'user/:name', to: 'profile#show', as: :profile
+
   mount Mastodon::API => '/api/'
+
+  root 'home#index'
 end